Spray droplet analyzer

ABSTRACT

Apparatus for analyzing fluid spray patterns for evaluation of characteristics of the spray and of the spray nozzle comprising a video system for counting the number of various size droplets in a specified view volume of the spray and a positioning and computer system cooperative with the video system for moving the nozzle to various positions and for performing a complete analysis of the fluid spray pattern. A three axis closed loop positioning system is used to control the instantaneous location of the fluid spray within a spray chamber and a conventional vidicon pick up tube receives images of fluid droplets at the particular view volume, the illumination being provided by an inline xenon flash tube. Multiple readings of both the number and size of droplets in a particular view volume are made, the droplets being recognized by the intersection of the images with the scanning lines of the vidicon tube, and the averaged totals are retained in appropriate readout registers. The information of each view volume is recorded on paper tape together with the location of the view volume for further computation and a complete analysis of the spray pattern. The spray chamber further includes a shield for the vidicon tube aperture wherein a continuous airflow prevents condensation of the fluid on the viewing glass.

United States Patent [72] inventors Harold C. Simmons Richmond Hts;

John H. Gang, Chesterland, both of Ohio 211 Appl. No. 777,057 [22] Filed Nov. 19, 1968 [45] Patented Sept. 28, 1971 [73] Assignee Parker-lianniiin Corporation Cleveland, Ohio [54] SPRAY DROPLET ANALYZER 14 Claims, 7 Drawing Figs.

[52] US. Cl 356/102 [51] ..G01n 15/02 [50] 356/36, 102, 103; 350/63 [56] References Cited UNITED STATES PATENTS 2,433,856 1/1948 Marihart 350/63 x 3,321,265 5/1967 Clave et al. 350/63 2,997,597 8/1961 356/102X 3,098,931 7/1963 356/102X 3,183,351 5/1965 gig/83.3 3,275,744 9/1966 356/102 3,461,280 8/1969 356/102 Primary ExaminerRonald L. Wibert Assistant Examiner-Conrad Clark AttorneyOberlin, Maky, Donnelly & Renner ABSTRACT: Apparatus for analyzing fluid spray patterns for evaluation of characteristics of the spray and of the spray nozzle comprising a video system for counting the number of various size droplets in a specified view volume of the spray and a positioning and computer system cooperative with the video system for moving the nozzle to various positions and for performing a complete analysis of the fluid spray pattern. A three axis closed loop positioning system is used to control the instantaneous location of the fluid spray within a spray chamber and a conventional vidicon pick up tube receives images of fluid droplets at the particular view volume, the illumination being provided by an in-line xenon flash tube. Multiple readings of both the number and size of droplets in a particular view volume are made, the droplets being recognized by the intersection of the images with the scanning lines of the vidicon tube, and the averaged totals are retained in appropriate readout registers. The information of each view volume is recorded on paper tape together with the location of the view volume for further computation and a complete analysis of the spray pattern. The spray chamber further includes a shield for the vidicon tube aperture wherein a continuous airflow prevents condensation of the fluid on the viewing glass,

PATENTEDSEP28|97| 3.609.043

INVENTOR S HAROLD C. SIMMONS JOHN H G/MG ATTORNEYS SPRAY DROPLET ANALYZER This invention relates to particle counting devices and more particularly to apparatus for determining the size, count and distribution of droplets in a fluid spray pattern for analysis of such spray pattern.

In fluid spray applications and in jet engine technology in particular, it is desirable to inspect the projected spray to determine whether a proper nozzle operation is being obtained and an efi'icient utilization of the fluid material is being made. In jet engines this is of particular significance since combustion of the fluid takes place and it is desirable to know the degree of atomization of fluid, the configuration of the spray pattern and its orientation within the combustion chamber, all relating to some extent to rate of combustion and efficient utilization of the fuel. Not only is this knowledge useful in the design of new nozzle configurations or combustion chambers, but also in the production of an established design where quality control must be maintained. Similarly, because of the multiplicity of nozzles in a single engine, balanced or even distribution of fluid is of importance. Under the high reliability requirements of todays technology, it is commonplace not only to test each nozzle in a production lot, but also to perform similar tests during various stages of manufacture. It is apparent that apparatus which will perform such measurements in a rapid and highly reliable manner is required in this industry.

In the past it has been usual to rely on the visual inspection of highly trained technicians to determine some characteristics of fluid spray patterns, but this being a subjective technique is prone to great variations and incidence of error. It is also clear that by this method it would be extremely difficult to evaluate the degree of atomization of the fluid, the cross-sectional configuration of the spray and the comparison of patterns between nozzles of different types. Another standard test for determining droplet size distribution in a particular spray pattern has been the wax technique wherein liquid 'wax is sprayed from the nozzle to form droplets which solidify and which may be sorted and counted by successive screenings. Such method is extremely tedious and time con- 'suming and subject, at least, to the drawback that there may be a wide disparity between the characteristics of liquid wax and volatile fluids used as fuel in jet engines and the like. A more recent technique has been the photographic method whereby a series of photographs are made by means of short duration flash techniques, the pictures thus obtained being examined visually and measurements made of the size of the individual droplets. This latter technique does have the advantage of a capability for examining a very small portion of the total spray pattern by means of the optical system and further gives some indication of the motion of the various particles when succeeding photographs are correlated and analyzed. This technique is, of course, also very time consuming and impractical for high production rates, requiring also a considerable expenditure for the materials utilized in the and detailed measurements and analyses can be performed on the spray patterns. Here, television techniques and high-speed information handling are utilize to provide sufficient information in a short interval of time so that an accurate determination of the spray pattern and thus the nozzle construction may be realized. A conventional television vidicon tube is used as the sensing element in this system and the tube monitors the images of a specific view volume of the spray pattern for conversion to electrical signals. A high-speed flashtube provides illumination for the scene, the duration of the flash being sufficiently short as to efiectively stop droplet motion and the persistence of the sensing tube being sufficiently long to provide an interval for the conversion of the images into electrical signals.

Readout of the vidicon tube takes place by conventional scanning techniques and the resulting output signal provides an indication of the number of droplets encountered in a particular sample interval and also the size of the droplets as determined by the interception of a number of scanning lines. Droplet counts are electrically sorted and distributed into a group of six scaling registers after an electronic conversion has been applied to accommodate the differences in view volume encountered for different size particles. A number of samples are taken at a particular view volume location so that the total count may be representative of the average configuration of the spray at that location. Specialized electronic circuitry is utilized for detecting out of focus images to isolate the view volume and also to accommodate a plurality of imagesoccurring on previously intercepted scanning lines.

A three-axis closed loop position control system is utilized for mounting the nozzle within the spray chamber and for positioning the nozzle and thus the spray cone in relation to the viewing system. Such positioning system may be manually controlled or automatically programmed for performing a complete analysis of a fluid spray pattern and in either event provides a read-out signal of the instantaneous position of the nozzle for a particular sample interval. Position information as well as droplet size and number information is recorded on paper tape and such information is then available for further interpretation. In a symmetrical nonrandom spray cloud, as described in this embodiment of the invention, measurement of droplet size at a large number of locations, predetermined in the spatial configuration, will supply sufficient information for analysis of the total spray.

In this system an electronic computer is utilized to perform further computations on this output information, for example, for the purpose of reconstruction of the configuration of the spray pattern from the discrete information received. The computer includes a program for conversion of the information relating to a specific view volume in a plane of symmetry into information indicative of the total droplets in a particular spray or the distribution of the density of droplets as related to the distance of the view volume from the central axis of the spray pattern. Further, selected qualitative determinations of a nozzle can be performed by means of other computer programs including a simple reject or pass determination for production quantities based on the analysis of the spray.

Therefore, it is a primary object of this invention to provide apparatus for analyzing fluid spray nozzles by means of rapidly and accurately measuring the number, size and distribution of droplets in the spray pattern of the noule.

It is another object of this invention to provide apparatus for analysis of fluid spray patterns wherein a sampling is made of selected portions of the spray and measurements are performed utilizing computer techniques.

It is still another object of this invention to provide apparatus for analyzing nozzle spray patterns wherein an instantaneous measurement of the pattern or a sequential measurement of selected portions of the spray is performed in a completely automatic or semiautomatic mode of operation.

It is a further object of this invention to provide nozzle spray analysis apparatus in which discrimination of particle sizes is realized for grouping along predetermined size ranges.

It is a still further object of this invention to provide nozzle spray monitoring apparatus which performs measurements under actual use conditions of the nozzle, involving no disturbance of the spray pattern and utilizing high-speed video techniques.

It is yet another object of this invention to provide pattern spray analysis apparatus which utilizes a computer programmed to correlate and compensate the discrete measurements of the system and to provide an indication of the quality of the nozzle under test.

It is still a further object of this invention to provide a spray analyzer which automatically produces a recorded output of selected spray configuration information for purposes of analysis or for comparison with predetermined standards of quality.

It is a yet further object of this invention to provide spray analysis apparatus which includes a closed loop positioning system for the nozzle under test whereby selected portions of the spray pattern can be automatically brought under scrutiny of the measuring system.

It is a still further object of this invention to provide in fluid spray analyzing apparatus a novel fog prevention shield which assures an unobstructed view of the interior of a test chamber.

Other objects and advantages of the present invention will become apparent as the following description proceeds.

To the accomplishment of the foregoing and related ends, the invention, then, comprises the features hereinafter fully described and particularly pointed out in the claims, the following description and the annexed drawings setting forth in detail certain illustrative embodiments of the invention, these being indicative, however, of but a few of the various ways in which the principle of the invention may be employed.

Referring now to the drawings:

FIG. 1 is an environmental view of the nozzle test stand showing the relation of the video system, the nozzle positioning system and the control console;

FIG. 2 is a partial elevational view of a portion of the test stand showing the novel shield construction in cross section;

FIGS. 3 and 4 are respectively plan and elevational views with parts broken away of the three-axis positioning system and mounting mechanism for the nozzle under test;

FIG. 5 is a logic diagram in block form of the video and information handling control system;

FIG. 6 is a logic diagram in block form of the control system for the three-axis closed loop positioning system; and

FIG. 7 is a schematic diagram of the fluid spray analyzing system showing a selected view volume of the fluid spray pattern.

Referring now to FIG. 1, there is shown a test unit 1 for analyzing the spray patterns of nozzles comprising a spray chamber 2 mounted on a free standing console 3, the latter containing fluid pumps, the fluid for test purposes and certain hydraulic controls which may be manually activated by the operator for any test operation. The spray chamber 2 comprises a housing of boxlike configuration having transparent front and rear surfaces 4 for visual inspection of the test under performance and substantially closed sidewalls 6. The upper portion of the spray chamber 2 is open for access to the interior thereof and supports a three-axis positioning mechanism shown generally at 8 and a nozzle clamping device for mounting a nozzle in a vertical position so that the spray from the noule may be directed downwardly into the chamber for test purposes. Suitable hoses (not shown) connect the nozzle with the fluid under pressure located in the console 3 and drains are provided in the bottom of the chamber 2 for recirculation of he fluid.

A pair of triangular supports 9, l0 fabricated of any suitable material are mounted on the leftand right-hand sides of the spray chamber 2 to serve as platforms for the light source 11 "and vidicon pickup tube 12 comprising a portion of the video sensing system. Both the light source 11 and the vidicon tube 12 are mounted in explosion proof housings and communicate with the interior of the spray chamber 2 by means of aligned apertures 13 in the leftand right-hand walls 6 of the chamber. Suitable scaling is provided for the video components at the apertures 13, most conveniently by glass windows mounted in the walls 6 of the spray chamber. As depicted in FIG. 2, a special shield is provided at least in association with the vidicon tube housing 12 for preventing fogging of the aperture and inconsistent test results. Such apparatus forms a part of this invention and will be described in greater detail hereinafter.

Both the vidicon tube 12 and the light source 11 are connected to the control cabinet 15 by way of cables 16 for transmitting control and information signals therebetween. Similarly, components of the positioning system 8 are coupled into the control cabinet 15 by way of cables (not shown) for transfer of nozzle position information. The control cabinet 15 houses most of the electronic circuitry for this analyzer system and includes on the front panel thereof a group of six scalers 18 which register and provide a visual indication of the number of droplets in predetermined size ranges for any measured view volume. Directly below the output indicators for the scalers 18 is a tape punch mechanism 19 comprising a conventional takeup and supply reel and tape punching device. As described in greater detail hereinafter the total counts of the scalers 18 are recorded on paper tape by the tape punch mechanism 19 together with nozzle position information evidencing a particular selected view volume of the spray pattern which is being sampled. Mounted on top of the control cabinet 15 is a TV monitor 20 connected to and providing a representation of what is being sensed by the vidicon tube 12 and further providing specific information as to proper operation of the system which then is immediately available to the operator.

Referring now to FIG. 7, a more graphic description of the operation of this system may be obtained. Shown schematically is a nozzle 21 producing a spray pattern 22 in one position as depicted by the solid lines and in a second position by dashed lines and the reference numerals 21a, 22a. The light source 11, which is a xenon flashtube, and the vidicon pickup tube 12 of the video system are linearly aligned on either side of the spray pattern 22 to produce images of the droplets comprising the spray on the sensing face of the vidicon tube 12. Both the light source 11 and the pickup device 12 transmit and receive light through lens systems to isolate a specific portion of the spray pattern 22 for sampling purposes. Such selected portion of the spray 22 is defined as the view volume and is represented in FIG. 7 by the rectangular solid 24 shown in solid lines. In this form of apparatus, the view volume 24 is on the order of 1 cubic millimeter, being shown somewhat out of scale in FIG. 7 for purposes of clarity. It is apparent, however, that such view volume 24 represents only a relatively small portion of the total spray pattern 22 from a nozzle 21 under test.

For purposes of this description it can be considered that the fuel nozzle 21 produces an essentially hollow conical spray 22 of liquid droplets. This spray 22 is formed by forcing from the nozzle 21 a thin cylindrical or conical film of fluid which breaks up under the influence of external and internal forces into a cloud of droplets which then tends to retain the hollow conical form for a distance of several inches. The spray 22 consists of droplets moving at relatively high velocities which can range on the order of 50 feet per second and which may vary for different size droplets, generally being higher for the larger droplets. In such a spray, not only is the motion of the droplets of significance for evaluation purposes, but also the number of droplets and be physical size of same which are all interdependent in, for example, fuel combustion in a jet engine. On the order of a million droplets are instantaneously contained within a spray 22 within a distance of approximately 4 inches from the nozzle 21. By selection of an appropriate view volume 24 only several droplets need be under consideration at a particular sample interval which makes a system of this type practical. The large number of droplets within the spray, however, allows the use of statistical techniques appropriate to sampling a large population. Having some knowledge of spray configuration therefor allows the evaluation of a particular spray by a relatively small sampling of the total volume and accuracy of a particular view volume is assured by a relatively high number of repeated samplings to obtain an average value.

Further, the droplets range in size from about 10 through 400 microns for nozzles of this type with very few droplets less than l0 microns and very few more than 300 microns. The distribution of droplets in size is typically in a skewed Gaussian" form and measured data of this kind can be manipulated mathematically to provide results appropriate to combustion requirements. Therefore, it is entirely satisfactory to measure the apparent diameter of the individual droplets, which are approximately spherical, and collect the data in size classes.

Thus, as seen in FIG. 7, a typical analysis of a spray pattern 22 would consist of first locating the noule 21 in the position shown by the solid lines to locate the view volume 24 directly on the axis of symmetry 25 of the spray cone. At this location approximately 100 samples of the view volume 24 are monitored and averaged by the electronic circuitry to provide a quite accurate determination of the number and size of droplets in this view volume. Such information is accumulated in the scalers l8 and the total is provided as a visual or electrical output in each of six droplet size ranges at the control cabinet 15. At the completion of the sample interval the information contained in the scalers 18 is sequentially interrogated and utilized to operate the tape punch 19 to provide a permanent record for further computational purposes. Simultaneously, position information of the location of the view volume 24 with respect to the spray cone 22, as by the position of the nozzle 21 in relation to the spray chamber 2, is also recorded on the paper tape. Succeeding samples may then be taken of the spray 22 by movement of the nozzle 21 to a new position and a recycling of the sampling circuitry.

As depicted in FIG. 7, a second measurement may be obtained of the spray 22 by movement of the nozzle 21 to the position shown at 21a to produce the spray pattern 22a, by a linear movement in the direction of the arrow 26 such that the view volume 24 while remaining in the same place in the spray chamber 2 and in relation to the light source 11 and vidicon tube 12, is now located on the periphery of the cone 22a.

This linear or radial measurement is most often performed in a number of steps depending on the accuracy of evaluation of nozzle performance required. In any event, it becomes clear that the number of droplets contained in a view volume 24 located at the central axis 25 of the cone as compared with that contained in a view volume located at the periphery of the cone represents a different proportion of information as to the total number of droplets in the cone at the particular plane is desired. Thus, some compensation must be made upon the information of a direct reading of the view volume 24 depending on the configuration of the spray pattern 22, the relation of the view volume therein and the results desired. Information of this type may be obtained from a computer 28 contained in the control cabinet which receives data from the punched paper tape or directly from the outputs of the scalers 18, for example, and which is programmed for the desired result.

For example, when it is desired to obtain data indicating the total number of droplets contained in the spray 22 in a certain plane of symmetry as depicted by the measurement technique described above and in FIG. 7, the information received of a particular view volume must be operated on by a factor of 2 pi times the radius of the view volume 22 from the central axis 25 of the cone to provide the total required. Such computation is readily accommodated by the computer 28 and may be performed as soon as the accumulated information of each view volume is available to provide an immediate indication of the quality of the spray or, alternatively, may be reserved for a later time when a complete analysis of the spray is performed.

Referring now to the FIG. 5 logic diagram of the video portion of this system, there is again shown the video tube detector 12 in association with the light source 11 and circuitry in block diagram form for converting video signals to a numerical count for storage by the tape punch 19. Much of the circuitry of this invention is of the conventional closed-circuit television type utilizing well-known video techniques for achieving a readout of the video tube 12. Thus, horizontal and vertical sweep circuitry as well as energizing and synchronizing circuits are not shown. However, it will be appreciated that the video tube 12 may be scanned at a 30 frames per second rate using 525 lines in the raster. An output signal from the video tube 12 is received on line 30 and includes horizontal and vertical synchronizing signals as well as the video signal, characterized by pulses corresponding to the interception of a droplet image by the scanning beam. Such output signal is applied in common to the horizontal and vertical sync separator circuit 31, the sync remover and video amplifier 32 and the video mixer 33.

In this embodiment of the invention, each sample of a particular view volume 24 consists of or 1,000 cycles of illuminating and sensing of the view volume 24 at the selection of the operator. Such sample provides an average indication of the number of droplets in the view volume over a period of time and avoids the randomness inherent in a limited sample arrangement. For purposes of description, it will be assumed that a IOO-cycle sample will be utilized and that the interval is timed by the sample timer 35 which is energized by a pulse applied at input line 36. Alternatively, timer 35 may be energized by the depression of the pushbutton 34 by the operator in a manual mode for test or setup purposes. Initiation of the sample timer 35 will energize the light source 1 l to cause illumination of the flashlamp in correspondence with vertical sync pulses received from the H 8:. V sync separator 31. The complete information handling or video signal processing, to be described, then occurs on each cycle or flash of the light source 11, until the l00-cycle sample is completed.

The sync separator 31 serves to detect the horizontal and vertical synchronizing pulses and applies both in common to the sync remover and video amplifier 32 and to the video detector 37 to prevent the transmission of the synchronizing pulses with the video signals. This conventional video technique prevents the overloading of circuits by the high-amplitude sync signals and the possible confusion with the low-level signals relating to the registration of droplet images. Thus, the signal received at the output 38 of the sync remover and video amplifier 32 is the pure video signal containing pulses corresponding to droplet images. Such signal is applied to the focus detector 39 and the video detector 37, the latter comprising a quantizing circuit which detects signals above or below a threshold level to provide an output signal on line 40 having pulses of fixed amplitude.

The focus detector 39 is a form of difierentiator circuit and determines in part the volume of the spray being viewed in any sample interval. Thus, for out of focus images or droplets which are either in front of or in back of the view volume 24 of interest, video signals of relatively low rise time will be realized and will be detected by the focus circuit 39 to prevent registration by the absence of an output signal on line 41. If the signals are of sufficient rise time, however, the output signal will be applied via line 41 to the video mixer 33 and as a conditioning signal to the sizing circuit 42 for channel 1 (shown in solid lines) and similarly to corresponding circuitry for channels 2 and 3, designated respectively by the dashed boxes 42!), 420.

In channel 1 (and similarly in channels 2 and 3) gating 44, look pulses loop 45 and sizing 42 circuits cooperate to sense the size of the droplets detected by the video tube 12 to supply counts to the appropriate size range. The quantized video signal on line 46 containing the information of each scan line of the raster is applied by way of the gating circuit 44 to the look pulse loop circuit 45 which generates an internal pulse for application back to the gating circuit 45 by way of line 48 each time droplet information is received. This internal pulse is delayed by exactly one horizontal line of the scan and is compared with subsequent video signal information on line 46 in an AND gate or coincidence circuit comprising the gating circuitry 44 to then provide a coincidence signal on line 49. In effect, then, when a droplet image is detected on a scan line, circuitry is activated to accept pulses occurring on the next succeeding scan in that same portion of the raster as displaced by one horizontal line. Each continuance of this comparison indicates continued scanning of the same droplet image and a single pulse for each scan line is applied by way of line 49 to the sizing circuit 42. When the image is completely scanned at succeeding video signal on line 46 will contain no information of a droplet and no further pulses will be generated on line 49. This condition will be detected, and the total count recorded in the sizing circuit 42 which is merely a counting circuit will be applied as a single pulse on one of the lines 50 to enter a single count in the appropriate droplet size range. Simultaneously the sizing circuit 42 will be reset for receipt of additional signals.

Provision is made for the receipt of multiple signals on the same scan lines by the additional identical circuitry of channels 2 and 3. Thus, once the circuitry for channel 1 has become energized by the receipt of a video signal indicating a droplet image, the activation of the look pulse loop 45 will, during the same horizontal scan, activate channel 2 to receive video information from line 46, as by a simple AND gate, and if necessary the same procedure will obtain to eventually activate channel 3 so that the receipt of up to three droplet images on the same scanning lines may be accommodated. Channels 2 and 3 provide output counts in the various size ranges from sizing circuits 42b, 42c identically as does channel 1 and as indicated, all outputs 50, 50b, 500 are joined respectively in the six OR gates 51 for the various size ranges. Output counts in the various size ranges then will be applied by way of conversion factor circuits 52 to individual sealers 55 which will accumulate and retain the count information.

It is significant to this invention that a standard view volume 24 may be maintained for an accurate determination of the density of the spray; however, it has been determined that a different View volume is effectively obtained for the different size droplets due to the depth of field of the lens system for the light source 11 and video detector 12 and the action of the focus detector 39, such that a larger view volume is obtained for larger droplet sizes. This variable view volume is compensated for in the conversion factor circuits 52 wherein a factor is applied to each incoming pulse from the OR gates 51 to apply a corrected number of pulses to the sealers 55.

The efiect of droplet size on view volume is determined experimentally by the introduction of test slides into the viewing system once the focus detector 39 has been stabilized at a particular setting. The test slide bearing the various droplet images is moved backward and forward in the viewing range until a determination is made as to when further counting of pulses is rejected by the focus detection circuitry. While the exact conversion factor is not necessary for an understanding of the teachings of this invention, the measured view volume does increase for the larger size droplets and accordingly the conversion factor circuits 52 for the larger size ranges must scale down the droplet count applied to the sealers 55 while that for the smallest droplet size range must be scaled upwardly to achieve a common basis. in fact, both an averaging for the total sample count of 100 cycles, as well as the view volume correction is applied in the conversion factor circuitry such that the total indication in the sealers 55 is a final determination representative of the density of droplets in the various size ranges on a common view volume basis. The conversion factor circuits 52 are simply pulse multipliers, presettable to provide a definite number of pulses to the sealers 55 for each pulse received from the OR circuits 51.

The vertical pulses obtained from the horizontal and vertical sync separator 31 control the discharge of the light source 11 such that after the completion of a full scan of the raster and a complete count and conversion of the droplet images in the view volume, the light source 11 will be triggered to initiate another scan of the view volume. Such cycling will be repeated until 100 scans have been obtained, this figure being determined in the sample timer circuit 35. In actual circuit operation, safeguard and certainty operations are included to improve the performance of the system but a detailed understanding of these techniques is not necessary for explanation of the teachings of this invention. However, for example, one such technique would involve the use of only every other scan of the raster for providing the droplet count indication, alternate scans being performed without illumination from the light source 11 and with the counting circuitry in an off condition so as to clear or erase the images recorded on the face of the vidicon tube 12.

As indicated previously, droplet movement is substantially stopped by the short duration flash of the light source 11 which is on the order of 0.5 microseconds. The persistence of the screen of the vidicon tube 12 is sufficient to maintain the droplet images for an interval of time sufficient for the scanning to be completed and as noted an additional scanning of the raster is performed to completely erase the image. In this rather short time interval and concurrent with the scan, droplet images are sensed and sorted and counts are distributed to the appropriate scaling registers. The view volume is sufficiently small so that only relatively few images are received, the system, however, having the capacity for accommodating plural images on the same raster lines as well as vertically separated images.

Further, provision is made for allowing the operator a continuous monitor of the operability and accuracy of the system as well as an aid for initial alignment by means of a visual signal at the screen of a TV monitor 56. Such closed-circuit television loop comprising the vidicon tube 12 and the monitor 56 is independent of the counting portion of the system and only general information is supplied. The monitor 56 receives images at the rate of 15 frames per second, and the droplet distribution in the view volume is continually changing so that an accurate determination by the operator is not possible except for test slides bearing stationary images; however, additional information is supplied in pulse form to provide bright images at the face of the monitor 56 to signal of operability of the system. Thus, the output of the vidicon tube 12 is connected directly to the video mixer 33 as is the output of the video detector 37. Further, the outputs of the look pulse loop 45 and the focus detector 39 are also applied to the video mixer 33 to introduce additional visual information. Therefore, along with the actual representation of the droplet image recognizable bright line associated therewith will provide infonnation as to the correct operation of the focus and look pulse loop circuitry as well as an indication of when a particular counting interval has been completed.

The completion of a sample interval or a -count cycle is determined by the sample timer 35 to change the state of the output signal on line 58 thereby preventing the application of further pulses to the conversion factor circuits 52 bymeans of switching conventional AND gates. The output signal on line 58 also provides an indication to the scanner control 60 to initiate readout of the system and recording of the information on paper tape. The scanner control 60 could be initiated as well manually by depression of the pushbutton 61 as a semiautomatic mode of operation is being utilized; however, normally the completely automatic mode described will be used. The scanner 62, shown in parts in H68. 5 and 6, comprises a form of stepping circuitry for sequentially interrogating the information contained in the sealers 55 and the nozzle position information and applying same digit by digit to the tape punch 19. Conveniently, the information output of the sealers 55 is in the binary coded decimal format such that a different digit of information may be recorded in each row of the paper tape which is stepped along in relation to the tape punch 19 in correspondence with the stepping of the scanner 62.

At the completion of the scanning and tape punch sequence, the scanner control 62 will generate a completion signal on line 64 which is directed to the command register 65 of the positioning system for the nozzle to move the spray pattern to a new position. Simultaneously with readout, the sealers 55 are reset so that the counting system will be prepared for receipt of new information in the next sample interval. After energization by the pulse on line 64 the positioning system will move the nozzle automatically to a new position and when all three axes have achieved position, a completion signal will be generated and directed to the sample timer on line 36 to initiate the next sample interval. it is clear that this automatic control loop for the complete system may be interrupted at any convenient point to provide a semiautomatic mode of operation and it may be convenient in some instances to provide a manual movement of the nozzle to a new position, retaining, however, the encoding of position information in form suitable for recording on paper tape or for utilization by the associated computer 28.

At the end of the sample interval, droplet count information is immediately available directly from the sealers 55 or from the paper tape once the scanner and punching sequence has been completed. In either event, the information on droplet size distribution may be operated on by the computer 28 to produce any desired result including a partial or complete analysis of the spray or nozzle. In this description of the invention, the information recorded on paper tape is entered into the computer 28 by means of a tape reader 65 of any suitable form for later analysis when all sample intervals have been completed for the particular spray pattern. As previously noted, it is desired to determine the total number of droplets in various size ranges in a particular plane of symmetry of the spray cone and such computation involves the use of information as to the number of droplets in a particular view volume together with information as to the position of the view volume with respect to the axis of symmetry 25 of the cone.

FIGS. 3 and 4 show in plan and elevational views the positioning apparatus 8 for locating the nozzle 21 in the spray chamber 2 in relation to the light source 11 and vidicon tube 12 having the optical alignment indicated by line 66. The positioning apparatus 8 comprises a mutually perpendicular threeaxis closed loop digital positioning system having the capability of orienting the spray of the nozzle 21 in any desired position in relation to the view volume 24 of the optical system. The apparatus comprises a base 68 of generally U-shape formed of plate material and adapted to be seated on top of the spray chamber 2 and to be retained in location by means of an abutment step 69 on the lower surface of the base 68 and conventional securing means so as to maintain a fixed orientation with respect to the walls 4, 6 forming the spray chamber 2.

Mounted on the baseplate 68 at approximately the corners of the spray chamber 2 are four upright members 69, 70 containing apertures therein for mounting of a guide shaft 71 and a drive shaft 72 for effecting movement of the nozzle 21 in an X or lateral direction with respect to the operator. The guide and drive shafts 71, 72 are mounted parallel to one another, the guide shaft 71 being a rod rigidly mounted in the uprights 69 by means of setscrews and the drive shaft 72 being threaded and rotatably mounted in the uprights 70 and prevented from lateral movement. A rear slide 74 is mounted on the guide shaft 71 by means of ball bushings 75 for movement in the X-direction and a front screw slide 76 is mounted on the drive shaft 72 by means of a trapped nut 78 which engages the threads of the drive shaft 72, to provide movement in the X-direction upon rotation of the drive shaft 72. A drive motor 79 is further mounted on the baseplate 68 by means of an angle bracket 80 and is connected to the drive shaft 72 by means of a rigid coupling 81 to impart rotation to the drive shaft 72 and thus effect the lateral or X-direction of movement to the slide shaft 76. Preferably motor 79 is of the DC servo-type for imparting rotation in either direction in response to an error signal of the closed loop positioning system which will be described in greater detail hereinafter. Further mounted in the upright 70 at the left-hand end of the drive shaft 72 as viewed in FIG. 4 and coupled thereto by a set of spur gears 81 is an encoder 82 or position indicating device which provides an electrical signal indicative of the instantaneous position of the screw slide 76 in relation to the drive shaft 72 and thus of the nozzle 21 with respect to the spray chamber 2. Again the encoder 82 may be of many different forms compatible with a closed loop positioning system but preferably as in this embodiment of the invention, is a binary coded decimal encoder providing a digital output representative of position.

As described in only general terms, the positioning mechanisms for the Y- and Z-axes are similar to that described for the X-axis and each mechanism effects linear motion along the respective axis utilizing guide and drive shafts, a motor and an encoder to effect a three-dimensional positioning of the nozzle 21 within the spray chamber 2. Mounted between the rear slide 74 and screw slide 76 for the X-axis are the guide shaft 84 and drive shaft 85 for the Y-axis in rigid and rotative mountings, respectively, thereby providing a rigid mounting for and insuring a parallel and simultaneous movement between the slides 74, 76. A platform 86 is mounted on the guide and drive shafts 84, for the Y-axis by means of bushings 87 and an entrapped nut 88 which cooperates with the Y drive shaft 85 to effect back and forth movement of the platform 86 in relation to the spray chamber 2. The Y-axis drive motor 89 is mounted on the screw slide 76 for the X-axis and is coupled to the Y-axis drive shaft 85 by means of a rigid coupling 90. Further, an encoder 91 is similarly mounted thereon and is coupled to the Y drive shaft 85 by means of a spur gear 92 arrangement for monitoring rotation of the drive shaft 85 and thus the Y-position of the platform 86. It will be apparent that the Y-axis motor 89 and encoder 91 are carried by the screw slide 76 for the X-axis laterally of the spray platform 2 but are relatively fixed in relation to the drive shaft 85 for the Y-axis.

Also mounted on the platform 86 is an upright plate 94 providing a mounting for a further plate 95 in parallel relation to the platform 86 and a mounting for the drive motor 96 for the Z-axis. Again a guide shaft 98 and drive shaft 99 for the Z- axis are mounted between the plate 95 and platform 86, the drive shaft 99 being coupled directly to the drive motor 96 and to the Z-axis encoder 100 by means of a spur gear system 101. The nozzle mounting bracket 102 comprising a generally L- shaped'bracket is supported on the guide 98 and drive shafts 99 by a similar arrangement of bushings 104 and entrapped nut 105 such that rotation of the Z-axis drive shaft 99 imparts a vertical or up and down movement, as viewed in FIG. 4, to the nozzle mounting bracket 102. Located in an aperture in the lower portion of the nozzle bracket 102 is an air-operated nozzle clamp 106 connected to an air pressure hose 108, for retaining the nozzle 2] under test. The nozzle 21 receives fluid under pressure from a supply hose 109 to develop a spray pattern 110 directed vertically and downwardly into the spray chamber 2.

Since the upper portion of the spray chamber 2 is open, it is relatively easy for the operator to substitute a different nozzle in the spray chamber merely by reducing the air pressure to the nozzle clamping mechanism 106 as by a switch on the console 3 and reclamp the new nozzle in position. It is clear that any portion of the spray 110 can be brought into the line 66 of the optical view volume of the testing system by the sequential or simultaneous movement of the three axes of the positioning system. It will be clear that all portions of the spray pattern 110 will be available for testing purposes as it will be remembered that the detection portion of the system is relatively insensitive to images outside of the view volume under study because of the focus detection circuitry and optical constants of the system, described in some detail previously, such that the system is capable of effectively looking through the spray 110 to analyze a remote portion thereof, if desired.

Further, it will be apparent to those skilled in the art that different types of positioning systems may be compatible with a testing system of this type wherein, for example, it might be desired to provide a control over the rotative orientation of the nozzle 21 with respect to the mounting bracket 102 or the spray chamber instead of or in addition to the three-axis positioning system described. Such additional control is well within the skill of those familiar with this art and may readily be accommodated in the system.

Referring now to FIG. 6, the three-axis positioning control system is described in block diagram form and its interrelation with the droplet counting system is indicated. Here, as far as possible, the same reference numerals will be used as indicated in FIGS. 3 and 4 to facilitate the association of the control system with the positioning apparatus.

At the start of any testing interval, it is necessary to position the nozzle 21 in a preferred location in relation to the spray chamber 2 and thus to the sensing system and such will be effected by initial information from the command register 65. In a completely automatic system such command register 65 may comprise a punched paper tape reader and storage device or alternatively, a card reader or where only a semiautomatic mode of operation is desired may comprise, for example, a

bank of thumbwheel switches manually settable by the operator; any of these devices preferably providing an electrical output in binary coded decimal form of the desired position in each of three axes for the nozzle 21 in the spray chamber 2. The command register 65 as well as other electronic circuitry for the positioning system may be housed in the control cabinet and coupled by way of cables to appropriate portions of the positioning apparatus 8. As previously described, each axis of the positioning system includes a drive motor 79, 89, 96 and an encoder 70, 91, 100 mechanically coupled thereto, the former effecting movement in the respective axis and the latter providing an output signal preferably in binary coded decimal form of the absolute position of the nozzle in that axis. In each axis, information from the command register 65 is combined with information from the respective encoders 70, 91, 100 in a subtractive manner in comparators 110-112 to provide error signals at the output lines 113-115 of the comparators for application to the respective drive motors. The error signals on lines 113-115 may be on analog form having a direction indication and preferably are positive or negative signals depending upon the relative difference of the input signals and are a zero signal when a comparison is attained or when the nozzle 21 has reached its desired position.

The drive motors 79, 89, 96 are responsive to the error signals, producing rotation in one direction for a positive signal and in the reverse for the negative signal and imparting no rotation for zero error signal. A completion circuit 116 comprising a three input AND gate is provided and is connected to lines 113-115 to receive the error signals for all three axes and is operative to provide a completion pulse on line 36 when all three axes have attained their desired positions as indicated by common zero error signals. In the automatic mode, such completion signal on line 36 will initiate the interval of the sample timer 35 and start the counting cycles. The outputs of the encoders 70, 91, 100 are further connected by way of lines 118-120 to the same scanner 62, described with reference to FIG. 5, such that at the completion of a counting interval after the scalers 55 have been scanned and the information contained therein recorded in the paper tape, continued scanning will interrogate the information provides by the encoders 70, 91, 100 to record such on the paper tape in close association with the count information. As noted, at the completion of the scanning interval when all necessary information as been recorded on the tape, a signal is generated on line 64 of the scanner control 60 and directed to the command register 65 to cause new information regarding the next position of the nozzle 21 in relation to the view volume in the analyzing sequence to be entered in the command register 65. When such new information in the command register 65 is applied to the comparators 110-112, different error signals in those axes in which movement is desired will be obtained on line 113-115 causing energization of the appropriate drive motors 79, 89, 96 and positioning of the nozzle 21 until, again,

all three axes attain a zero error signal and a completion pulse is generated at line 36 for initiation of the next sampling interval.

With reference to the test depicted in FIG. 7, wherein only a pure radial movement is desired, only the Y-axis of the positioning system will receive new information on succeeding sampling intervals to cause movement of the nozzle 21 from that depicted in solid lines to that position of the nozzle 21a depicted in dashed lines. In actual practice, such movement would be accomplished in a number of steps such that a series of view volumes 24 would be recorded extending the full distance of the radius of the spray cone 22, and perhaps beyond on either side to obtain a complete picture of the spray pattern. Movement of the view volume beyond the central axis of the cone may result in redundant information but this can be readily accommodated by the computer 28 programmed to reject all information between definite boundaries ascertained from the recorded information of the position encoders 70, 91, 100.

Referring now to FIG. 2, it is apparent that even though the system is highly versatile in being able to select a specified view volume within a total spray or cloud of droplets, even looking through a portion of a conical spray, for example, to view a remote volume, it is necessary that the viewing aperture 122 for the vidicon tube 12 be kept clear of spray and foreign materials since such will affect the accuracy of the system in preventing a sharply focused image. For this purpose, a shield arrangement is provided to prevent condensation and the like from forming at the viewing aperture. The shield comprises a ring 124 having a notch 125 at the inner periphery thereof for receipt of a circular piece of glass 126 and for clamping same across the viewing aperture 122 against the wall 6 of the spray chamber 2. The ring 124 is of resilient material and forms a lens clamp and seal for retaining the glass 126, which may be a lens forming a part of the optical system for the vidicon tube 12, against the chamber wall 6.

A cap 128 of rigid material and of cup configuration, having a flange 129 at the rim thereof is seated against the resilient ring 124 and drawn into engagement therewith by means of bolts 130 engaging the chamber wall 6. The cap member 128 further includes a tube 131 axially oriented at the center portion thereof for providing a vent 132 which communicates with the space 134 enclosed by the cap 128 and the interior of the spray chamber 2. The cap 128 further includes a tapped hole 135 at the outer periphery thereof which receives a piece of tubing 136 providing air pressure into the space 134. The inner end of the tubular member 131 is located closely adjacent the glass 126 such that a restriction is effected therebetween and a relatively high-velocity flow of air is directed across the face of the glass 126 and through the vent 132 of the tube 131 to the interior of the spray chamber 2. The vent 132 is of sufficiently large diameter so that the air flows at a relatively low velocity into the spray chamber 2 so as not to disturb the configuration of the spray from the nozzle under test.

Such shield device provides a relatively good seal between the interior of the spray chamber 2 and the face of the vidicon tube 12 by means of the resilient ring and the positive airflow and further prevents fogging of the glass 126 or the splashing of fluids thereon which would compromise the accuracy of the analyzer system. Further, where the glass 126 is a lens of the optical system, the shield provides an unobstructed view of the interior of the spray chamber 2 through the vent 132 of the tubular section 131.

We therefore, particularly point out and distinctly claim as our invention:

1. Apparatus for measurement of the distribution of droplets in a fluid spray comprising a spray chamber, a nozzle, means for supplying fluid under pressure to said nozzle to form a spray of droplets therefrom, the spray being directed into said chamber, means associated with said spray chamber for registering the quantity of droplets in several size ranges in a selected view volume of said chamber, the view volume being small in relation to the volume of said chamber and being of preestablished size, said registering means thereby providing indications of the density of droplets therein, means for positioning said nozzle with respect to said chamber, means associated with said positioning means for providing a signal representative of the instantaneous position of said nozzle, and means responsive to said signal providing means and said registering means for operating upon the information received therefrom to provide an indication of the spray configuration.

2. Apparatus as set forth in claim 1 wherein said operating means is a computer adapted to receive information from said positioning means and said registering means, said computer being programmed to operate upon said registering means information by a function proportional to the signal of said positioning means to provide output information related to the position of said nozzle within said spray chamber.

3. Apparatus as set forth in claim 2 wherein said positioning system is adapted to intermittently move said nozzle in a predetermined pattern in relation to said registering means whereby a portion of a plane of symmetry of the fluid spray from said nozzle is brought into association with said registering means to provide a series of droplet distribution measurements and said computer is programmed to operate upon such series of measurements related by the spatial symmetry of the fluid spray to provide indications of the total configuration of the spray.

4. Apparatus for the evaluation of the fluid spray of a nozzle wherein the number, size and location of droplets in the spray are monitored comprising a spray tank for mounting the nozzle under test and for receiving the spray therein, first and second aligned apertures in said tank, a light source associated with said first aperture for directing a beam of light into said spray tank to illuminate the fluid spray, a light sensing device associated with said second aperture, said sensing device being responsive to images of fluid droplets to provide electrical signals representative thereof, circuit means cooperative with said sensing device for converting the electrical signals to pulses representative of the number of droplet images received, in a plurality of channels representative of preselected sizes of droplets, means for altering the number of pulses in each channel by a factor related to the preselected sizes of the droplets, a plurality of sealers corresponding in a number to the number of channels of said circuit means and operatively connected to said altering means for accumulating the pulses and for providing digital representations of the number of pulses received, a positioning system for variably locating the nozzle in relation to said spray tank, said positioning system comprising a signal device for providing representations of nozzle positions, and means responsive to the representations of said sealers and said positioning system for providing indications of the fluid spray configuration.

5. Apparatus as set forth in claim 4 wherein said latter means comprises a computer programmed to operate upon the representations of said sealers by factors related to the representations of said positioning system to provide information of the spray configuration in a spatial frame of reference.

6. Apparatus as set forth in claim 5 wherein said positioning system comprises a mechanism for moving said nozzle linearly along a radius of a conical spray, and said computer is programmed to convert the representations of said scalers, received at a series of locations along such radius, to quantities representative of a symmetrical plane of the spray, by multiplication by the product of 2 pi and the radial dimension of the location from the central axis of the spray cone.

7. Apparatus as set forth in claim 4 further including a lens system associated with said light source and said sensing device for defining a specific view volume within said spray tank to which said sensing device is responsive, said positioning system being operative to locate various portions of the spray from the nozzle under test within the view volume, said light source being a fiash lamp for illuminating the view volume for an interval of time sufficiently short to substantially stop droplet motion and said sensing device being a video pickup tube having associated scanning circuitry for providing electrical signals of the images of droplets in the view volume as received at said tube.

8. Apparatus as set forth in claim 7 wherein said positioning system is a plural axis mechanism for locating any portion of the spray within the view volume.

9. Apparatus as set forth in claim 8 wherein said plural axis mechanism comprises three mutually perpendicular position systems, each said position system comprising a closed loop automatic movement system, an information program containing predetermined end locations for each of said move ment systems, means for applying said program to said movement systems to locate a portion of the spray at the view volume and means for sensing completed movement of said movement systems for operating said circuit means.

10. The method of evaluating a nozzle by measurement of the fluid spray therefrom comprising the steps of directing the spray from the nozzle into a spray chamber, isolating sample volumes of the spray at predetermined locations therein, such sample volumes being small in relation to the total spray, electronically counting the number of various size droplets in such sample volumes, modifying the number counts of the various size droplets by a factor related to the relative size of the droplets to obtain density indications of the spray on a common volume basis, and processing such density indications by a factor related to the spatial position of the sample volumes in relation to the total spray to provide an indication of the spray configuration.

11. Apparatus for analyzing a spray of fiuid droplets, comprising video sensing means for developing electrical signals representative of the number of droplets in a portion of the spray, a flashlamp for intermittently illuminating the spray for detection by said video sensing means, focus means for rejecting electrical signals from out of focus images, thereby to define view volumes of predetermined size for various size droplets, means for separating the electrical signals into ranges representative of different size droplets, scaler means for accumulating the electrical signals as counts of the number of droplets in each size range, means for modifying the count of each said scaler means as a function of the relative droplet size to provide indications of the number of droplets in a standard volume, and means for monitoring the instantaneous relative position of the spray and said video sensing means for evaluation of the total spray.

12. Apparatus as set forth in claim 11 wherein said modifying means comprises an electronic multiplier connected between said separating means and said sealer means and providing output pulses at a predetermined ratio for received electrical signals from said separating means.

13. Apparatus as set forth in claim 12 wherein said monitoring means comprises a servosystem for positioning the spray with respect to said sensing means, said servosystem comprising a transducer for providing electrical signals representative of such position.

14. Apparatus as set forth in claim 13 further including means for operating upon the counts of said sealer means as a function of the position signals of said transducer for evaluation of the total spray configuration from preselected representative samples thereof. 

1. Apparatus for measurement of the distribution of droplets in a fluid spray comprising a spray chamber, a nozzle, means for supplying fluid under pressure to said nozzle to form a spray of droplets therefrom, the spray being directed into said chamber, means associated with said spray chamber for registering the quantity of droplets in several size ranges in a selected view volume of said chamber, the view volume being small in relation to the volume of said chamber and being of preestablished size, said registering means thereby providing indications of the density of droplets therein, means for positioning said nozzle with respect to said chamber, means associated with said positioning means for providing a signal representative of the instantaneous position of said nozzle, and means responsive to said signal providing means and said registering means for operating upon the information received therefrom to provide an indication of the spray configuration.
 2. Apparatus as set forth in claim 1 wherein said operating means is a computer adapted to receive information from said positioning means and said registering means, said computer being programmed to operate upon said registering means information by a function proportional to the signal of said positioning means to provide output information related to the position of said nozzle within said spray chamber.
 3. Apparatus as set forth in claim 2 wherein said positioning system is adapted to intermittently move said nozzle in a predetermined pattern in relation to said registering means whereby a portion of a plane of symmetry of the fluid spray from said nozzle is brought into association with said registering means to provide a series of droplet distribution measurements and said computer is programmed to operate upon such series of measurements related by the spatial symmetry of the fluid spray to provide indications of the total configuration of the spray.
 4. Apparatus for the evaluation of the fluid spray of a nozzle wherein the number, size and location of droplets in the spray are monitored comprising a spray tank for mounting the nozzle under test and for receiving the spray therein, first and second aligned apertures in said tank, a light source associated with said first aperture for directing a beam of light into said spray tank to illuminate the fluid spray, a light sensing device associated with said second aperture, said sensing device being responsive to images of fluid droplets to provide electrical signals representative thereof, circuit means cooperative with said sensing device for converting the electrical signals to pulses representative of the number of droplet images received, in a plurality of channels representative of preselected sizes of droplets, means for altering the number of pulses in each channel by a factor related to the preselected sizes of the droplets, a plurality of scalers corresponding in a number to the number of channels of said circuit means and operatively connected to said altering means for accumulating the pulses and for providing digital representations of the number of pulses received, a positioning system for variably locating the nozzle in relation to said spray tank, said positioning system comprising a signal device for providing representations of nozzle positions, and means responsive to the representations of said scalers and said positioning system for providing indications of the fluid spray configuration.
 5. Apparatus as set forth in claim 4 wherein said latter means comprises a computer programmed to operate upon the representations of said scalers by factors related to the representations of said positioning system to provide information of the spray configuration in a spatial frame of reference.
 6. Apparatus as set forth in claim 5 wherein said positioning system comprises a mechanism for moving said nozzle linearly along a radius of a conical spray, and said computer is programmed to convert the representations of said scalers, received at a series of locations along such radius, to quantities representative of a symmetrical plane of the spray, by multiplication by the product of 2 pi and the radial dimension of the location from the central axis of the spray cone.
 7. Apparatus as set forth in claim 4 further including a lens system associated with said light source and said sensing device for defining a specific view volume within said spray tank to which said sensing device is responsive, said positioning system being operative to locate various portions of the spray from the nozzle under test within the view volume, said light source being a flash lamp for illuminating the view volume for an interval of time sufficiently short to substantially stop droplet motion and said sensing device being a video pickup tube having associated scanning circuitry for providing electrical signals of the images of droplets in the view volume as received at said tube.
 8. Apparatus as set forth in claim 7 wherein said positioning system is a plural axis mechanism for locating any portion of the spray within the view volume.
 9. Apparatus as set forth in claim 8 wherein said plural axis mechanism comprises three mutually perpendicular position systems, each said position system comprising a closed loop automatic movement system, an information program containing predetermined end locations for each of said movement systems, means for applying said program to said movement systems to locate a portion of the spray at the view volume and means for sensing completed movement of said movement systems for operating said circuit means.
 10. The method of evaluating a nozzle by measurement of the fluid spray therefrom comprising the steps of directing the spray from the nozzle into a spray chamber, isolating sample volumes of the spray at predetermined locations therein, such sample volumes being small in relation to the total spray, electronically counting the number of various size droplets in such sample volumes, modifying the number counts of the various size droplets by a factor related to the relative size of the droplets to obtain density indications of the spray on a common volume basis, and processing such density indications by a factor related to the spatial position of the sample volumes in relation to the total spray to provide an indication of the spray configuration.
 11. Apparatus for analyzing a spray of fluid droplets, comprising video sensing means for developing electrical signals representative of the number of droplets in a portion of the spray, a flashlamp for intermittently illuminating the spray for detection by said video sensing means, focus means for rejecting electrical signals from out of focus images, thereby to define view volumes of predetermined size for various size droplets, means for separating the electrical signals into ranges representative of different size droplets, scaler means for accumulating the electrical signals as counts of the number of droplets in each size range, means for modifying the count of each said scaler means as a function of the relative droplet size to provide indications of the number of droplets in a standard volume, and means for monitoring the instantaneOus relative position of the spray and said video sensing means for evaluation of the total spray.
 12. Apparatus as set forth in claim 11 wherein said modifying means comprises an electronic multiplier connected between said separating means and said scaler means and providing output pulses at a predetermined ratio for received electrical signals from said separating means.
 13. Apparatus as set forth in claim 12 wherein said monitoring means comprises a servosystem for positioning the spray with respect to said sensing means, said servosystem comprising a transducer for providing electrical signals representative of such position.
 14. Apparatus as set forth in claim 13 further including means for operating upon the counts of said scaler means as a function of the position signals of said transducer for evaluation of the total spray configuration from preselected representative samples thereof. 